The goals o the proposed research are to (1) improve methods for disease control in Rana catesbeiana; (2) improve upon artificial breeding in laboratory-reared bullfrogs and (3) continue selection of laboratoy-reared bullfrogs for defined characteristics with emphasis on improving growth rates. The study will emphasize the following: 1. To refine techniques currently used to ovulate bullfrogs by: a. varying the time of injecting bullfrog pituitaries plus progesterone over a 24 hour period in order to determine if circidian rhythms impact ovulatory responses. b. determining if cycling temperature and photoperiod will enhance growth and reproductive development in females. c. additional testing to determine if high correlations observed between ovulatory responses and a defind morphometric index can be consistently produced. d. further determining the interacting role of photoperiod, temperature, and nutrition to induce gonadal recrudescence after initial laboratory-induced ovulation. 2. Continuing efforts to establish defined strains of bullfrogs by appropriate matings emphasizing rapid growth. 3. To further determine the effect of culture water pH and calcium on larval diseases and abnormalities. 4. To prepare and determine the protective effectts on bullfrog larvae of toxoids made from partially purified aerolysin. 5. To determine whether or not nutritional immunity can be used as an effective control method for the family of opportunistic pathogenic bacteria that cause disease in bullfrogs.